This invention relates to an object sensing system for sensing an object approaching an automatic swing door and, more particularly, to such system employing sensors which measure the distance to an object by triangulation.
An example of an object sensing system for an automatic swing door of the type described above is disclosed in WO97/42465 published on Nov. 13, 1997, xe2x80x9cA METHOD FOR THE DETERMINATION OF THE DISTANCE AND THE ANGULAR POSITION OF AN OBJECTxe2x80x9d. The sensing system disclosed in this international application has a sensor disposed on a swing door at a location near a lower hinge. The sensor is driven to emit a plurality of light beams in the horizontal and diagonally upward directions at each of door positions to which the swing door rotates or swings from an open or closed position of the door. The door positions are spaced by a predetermined angle from adjacent door positions. The light beams are reflected from some object, and the distance of the object from the sensor is measured based on the reflected light beams. The measurement at each door position is compared with a reference value predetermined for each door position. If the measurement is equal to the reference value for a particular door position, it is judged that the reflected light is from a stationary object near the door from the beginning and that there is no object approaching the door. If the measurement is not equal to the reference value, the reflected light is judged to be from an object other than the stationary object, which may be an object approaching the door. In this manner, the sensor judges that there is an object approaching the door. The reference value for each door position is determined based on light beams reflected from a stationary object, for example, a guard rail and plant pots to which light beams are directed from the sensor at that door position.
Since the sensor emits light beams in the horizontal direction and in the diagonally upward direction, there may be no stationary object that reflects the light beams emitted for the determination of reference values at some door positions. Accordingly, it may happen that such reference values would not be prepared for all of the door positions and that an object approaching the door would not be detected at some door positions. It may sometimes happen that when the swing door is swung for preparing the reference values, there is an object moving at a location away from the door. Since the light beams are emitted in the horizontal and diagonally upward directions, there is a possibility that the emitted light beams may be reflected from such object. The reliability of reference values prepared based on the light beam reflected from such object is low. Since the reference values are formed from reflected light from stationary objects, they are affected by the state of the reflecting surfaces of the stationary objects and, therefore, may not be stable.
An object of the present invention is to provide an object sensing system for use with an automatic swing door with reference values having increased reliability so that the sensing system can detect an object with higher reliability.
Another object of the present invention is to provide an automatic swing door which can be installed properly with reduced possibility of error in installing the sensing system.
An object sensor for use with an automatic swing door according to the present invention includes a light emitter and a distance detector which are disposed on a door surface of a swing door. At each of plural angularly spaced door positions, the light emitter emits a light beam toward a floor where the swing door is installed. The distance detector receives the emitted light as reflected from a reflecting object and develops an output signal having a value representing the distance of the object from the distance detector. A control unit makes a judgment based on the value of the output signal of the distance detector as to whether or not the object is approaching the door surface. The control unit stores therein the value of the distance detector output signal representing the distance of the floor from the distance detector, as a reference value. With respect to the reference value, a dead zone covering a range of from the floor to a predetermined height is set. The control unit judges that the object is an object approaching the door surface when the value of the distance detector output signal is outside the dead zone.
The value of the distance detector output signal developed at the closed position of the swing door may be used as the reference value for each door position.
The value of the distance detector output signal developed at each door position may be used as the reference value for that door position.
The dead zone may be set with respect to each of the reference values for the respective door positions of the swing door.
The light emitter may emit a light beam a plural number of times at each door position to thereby cause the distance detector to develop the same number of output signals. In this case, the values of the output signals of the distance detector are averaged to provide the reference value for that door position.
The light emitter may emit a light beam a plural number of times at each door position in both opening and closing strokes or operations of the swing door, and the values of the output signals developed by the distance detector in each of the opening and closing strokes of the door are averaged. The average at a particular door position obtained during the opening stroke and the average at the same door portion obtained during the closing stroke are averaged to provide the reference value for that door position.
The sensor may be disposed on each of the xe2x80x9capproachxe2x80x9d and xe2x80x9cswingxe2x80x9d side surfaces of the swing door. The approach side of the door is the side that an object or a person can approach in order to pass through the door, and the swing side is the side of the door to which the door swings open. The sensors on the approach and swing side surfaces of the door are connected to communicate with each other. Each of the sensors has a switch. Each sensor is arranged such that when the switch of that sensor is operated, that sensor can automatically recognize itself to be an approach side sensor or a swing side sensor and develops a predetermined sensor type identification signal. The sensor type identification signal developed by one of the sensors is sent to the other sensor, and the other sensor automatically knows its sensor type. For example, if the sensor of which the switch is activated is the approach side sensor, the other sensor recognizes itself as the swing side sensor upon receipt of the sensor type identification signal supplied from the approach side sensor. Each sensor, after automatically recognizing its own sensor type, executes a program corresponding to the sensor type.
The program corresponding to the sensor type may be a program for preparing reference value data for use in determining the presence or absence of an object approaching the automatic swing door at each of the door positions.
The sensor whose switch is operated may be the approach side detector.
Each of the sensors may include an alarming unit which can operate for a predetermined time period following the activation of the switch to alarm a worker installing the sensors so that he or she can go out of the path the door swings to avoid collision with the door.